Saskatchewan labour groups are arguing some of the provinces labour laws are unconstitutional before the Supreme Court of Canada on Friday. (CBC)

Labour groups will square off against the Saskatchewan government and business at the Supreme Court of Canada today in a dispute over changes to Saskatchewan's labour laws proposed in 2008.

The Saskatchewan Federation of Labour says Bill 5, Saskatchewan's essential services law, and Bill 6, which involves changes to the former Trade Union Act, are in violation of the Charter of Rights and Freedoms.

The essential services law restricts which public sector workers can walk off the job during a strike.

The Saskatchewan government says it's similar to laws in effect in other provinces and will be used to ensure public safety during labour disruptions. However, unions say the law makes it possible to declare so many employees "essential" that it undercuts their ability to bargain collectively.

Unions also say the Trade Union Act changes make it tougher to form unions in the first place, by raising the threshold of voting workers required to get a certification vote and by eliminating automatic certification in cases where 50 per cent of workers sign union cards in favour of secret ballot votes in all cases where the threshold is met.

The province says the changes make the laws more democratic and ensure public safety.

The unions had a partial victory at the Court of Queen's Bench level when a judge ruled in their favour on essential services, but the Appeal Court of Saskatchewan reversed that and dismissed both their cases.

The Supreme Court of Canada is expected to hear arguments for and against why the right to strike should be enshrined as a Charter-protected right.

In addition to the Saskatchewan participants in the case, labour groups, provincial governments and businesses from across Canada are intervening in today's proceedings.